It is the aim of the present randomized clinical multicenter trial to compare 2 different treatment protocols of a combined perio-regenerative and orthodontic therapy in advanced periodontitis patients with intrabony defects and pathologic tooth migration in order to establish whether one treatment modality is superior to the other with regard to clinical outcomes. A total of 46 patients will be enrolled and randomized into 2 treatment groups that differ by the time point of initiation of orthodontic therapy (early: 4 weeks vs. late: 6 months following regenerative periodontal surgery).